How Much Magnesium Per Day? A UK Dosage Guide
Magnesium is one of the few supplements almost everyone agrees is worth paying attention to. What almost nobody agrees on is the number. Ask how much magnesium per day you actually need and you will get answers ranging from 200mg to 800mg, often from sources that sound equally confident.
The confusion is not really about the dose. It is about which number a label is quoting.
Here is the official UK figure, the one measurement that determines whether a supplement delivers what it claims, and how to work out what you are genuinely getting.
How Much Magnesium Per Day Do UK Adults Need?
The Nutrient Reference Value for magnesium in the UK and EU is 375mg per day. That is the figure used on supplement labels to calculate the percentage NRV you see on the back of a pack.
Most of that should come from food. Leafy greens, nuts, seeds, wholegrains, legumes and dark chocolate are all reasonable sources, and a varied diet built around them goes a long way.
In practice, diets short on those foods leave a gap — which is where supplementation comes in, topping up rather than replacing what you eat.
One caution before the numbers: more is not better. High doses of supplemental magnesium, particularly in poorly absorbed forms, commonly cause digestive upset. The NRV is a reference point, not a target to exceed.
Elemental Magnesium: The Only Number That Matters
This is the single most useful thing to understand about magnesium labels, and it explains most of the confusion about how much magnesium per day you are really taking.
Magnesium never appears on its own in a supplement. It is always bound to something else — glycine, citric acid, malic acid, oxide — forming a magnesium salt. The weight of that whole compound is much greater than the weight of the magnesium inside it.
So a label advertising "1500mg magnesium citrate" is quoting the compound. The elemental magnesium — the mineral your body actually uses — might be a fifth of that.
A trustworthy product states both. Nutrian Calm+ supplies 1617mg of magnesium salts, delivering 350mg of elemental magnesium per serving — 93% NRV. When you compare products, compare the elemental figure or you are not comparing like with like.
Key Benefits of Getting Enough Magnesium Per Day
Magnesium is a mineral with a substantial list of authorised EU and UK health claims, which makes it unusually well-evidenced ground.
Tiredness and fatigue. Magnesium contributes to a reduction of tiredness and fatigue, and to normal energy-yielding metabolism.
Muscle function. Magnesium contributes to normal muscle function and to normal protein synthesis — relevant if you train regularly or spend your day on your feet.
Nervous system and psychological function. Magnesium contributes to normal functioning of the nervous system and to normal psychological function.
Bones, teeth and cells. Magnesium contributes to the maintenance of normal bones and teeth, to electrolyte balance, and has a role in the process of cell division.
Calm+ also contains 240mg of KSM-66® full-spectrum ashwagandha root extract per serving — an ingredient that deserves addressing directly rather than in a footnote.
Ashwagandha Benefits: What We Can and Cannot Tell You
Search ashwagandha benefits and you will find a great deal written about it. Very little of that can lawfully be repeated by a UK supplement brand, so here is our position, stated plainly.
KSM-66® is a branded full-spectrum ashwagandha root extract (Withania somnifera), produced by a green-chemistry process that uses no alcohol or chemical solvents and standardised to 5% withanolides. It is root-only, rather than the cheaper leaf-and-root material used in some products. Calm+ supplies 240mg per serving.
Those are facts about the ingredient. What we cannot do is attach an outcome to them. Ashwagandha holds no authorised EU or UK health claim — not for stress, not for sleep, not for mood — so no brand is permitted to tell you what it does, and we are not going to imply it around the edges either.
We include KSM-66® because it is the most extensively researched branded ashwagandha extract available and because customers ask for it by name. Anything you read about ashwagandha benefits elsewhere is not a claim Nutrian makes.
Magnesium Citrate vs Glycinate: Why the Form Changes the Dose
Two supplements can state the same elemental magnesium and still behave quite differently, because absorption varies by form.
Magnesium oxide is the cheapest and by far the most common in budget tablets. It carries a high elemental percentage but is poorly absorbed, and is the usual culprit behind digestive complaints.
Magnesium bisglycinate is chelated to the amino acid glycine, which makes it well absorbed and notably gentle on digestion.
Magnesium citrate is bound to citric acid — well studied and readily taken up by the body.
Magnesium malate is bound to malic acid, a compound that appears in the body's own energy cycle.
Calm+ uses the latter three together rather than relying on any single form, with no magnesium oxide as the main source. The serving is two capsules daily, taken after food — which is also why a 60-capsule pack is a full month rather than two.
Magnesium for Sleep: What the Authorised Claims Actually Cover
Magnesium for sleep is among the most-searched supplement phrases in Britain, so it deserves a straight answer rather than a quiet omission.
Sleep is not among magnesium's authorised health claims. No UK or EU brand is permitted to present magnesium as a sleep supplement, and Calm+ is not sold as one.
What magnesium is authorised for is set out earlier on this page: tiredness and fatigue, energy-yielding metabolism, muscle function, nervous system function, psychological function, protein synthesis, electrolyte balance, bones and teeth, and cell division. That list is the whole of what any honest label can stand behind.
On timing, which is usually the real question behind the search — there is no absorption argument for evening over morning. The serving is two capsules after food, and most people anchor that to whichever meal they never skip. Take it at the time you will actually remember.
What to Take With Magnesium
Magnesium works best as part of a foundation rather than in isolation.
Multi+ Multivitamin covers the wider spread of vitamins and minerals, including vitamin D, which contributes to the maintenance of normal bones and to normal muscle function — the same two areas magnesium supports, which makes them natural companions.
B Complex+ is the other sensible pairing. Vitamin B6 contributes to normal energy-yielding metabolism and to normal functioning of the nervous system, and vitamin B12 contributes to the reduction of tiredness and fatigue — reinforcing the areas where magnesium's own authorised claims sit.
Keep eating the greens, nuts and seeds regardless. A supplement is a top-up, not a replacement.
Who Should Take a Magnesium Supplement?
It suits adults whose diets are light on magnesium-rich foods, people with physically demanding routines or regular gym habits, and anyone who has tried a basic magnesium tablet and found it harsh on their stomach.
It is not suitable for children, or for women who are pregnant or breastfeeding. If you take prescribed medication or have reduced kidney function, speak to your GP or pharmacist first — the kidneys regulate magnesium levels, so this matters more than with most minerals.
Take two capsules daily after a meal, with water, rather than on an empty stomach. Consistency matters more than the time of day.
The Short Answer
How much magnesium per day? 375mg NRV, mostly from food, with a supplement covering the shortfall — and judged on elemental magnesium, not compound weight.
Nutrian Calm+ delivers 350mg of elemental magnesium (93% NRV) from three bioavailable forms, with KSM-66® ashwagandha, in vegan capsules made in Britain to GMP standards. Packs start at £8.99 for a one-month supply.
Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle. Consult your doctor if pregnant, breastfeeding or taking medication.